1. Field of the Invention
The present invention relates to a stereoscopic image display apparatus and a stereoscopic image producing method.
2. Related Art
A method of recording a stereoscopic image by using some method and reproducing it as a stereoscopic image is known. This method is called integral photography (hereafter referred to as IP method as well) or light ray reproduction method, and a large number of parallax images are displayed in this method. It is supposed that an object is viewed with left and right eyes. When a point A located at a short distance is viewed, an angle formed by the point A and the left and right eyes is denoted by α. When a point B located at a long distance is viewed, an angle formed by the point B and the left and right eyes is denoted by β. The angles α and β vary depending upon the position relation between the substance and the viewer. The difference (α−β) is called binocular parallax. Human being is sensitive to the binocular parallax and is able to conduct stereoscopic viewing.
In recent years, development of stereoscopic image display apparatuses without glasses has been promoted. Many of them use the ordinary two-dimensional display device (hereafter referred to as 2D display apparatus). Some optical plate is placed on the front or back of the two-dimensional display device, and the binocular parallax described above is utilized. Light rays can be made to appear to be illuminated from objects located several cm before and behind a display face of the two-dimensional display device when a viewer views the display face, by controlling angles of the light rays illuminated from the two-dimensional display device with the optical plate. This is because it has become possible to obtain an image which is high in definition to some degree even if light rays of the two-dimensional display device are distributed to several angles (called parallaxes), owing to implementation of the two-dimensional display device having a higher definition.
In the display apparatus of the integral imaging (abbreviated to II), light rays illuminated from one lens correspond to the number of element image groups, and the number is called number of parallaxes. In each lens, parallax rays are illuminated into equal distance angle distribution in a viewing angle independently of the viewer's position.
The resolution of a stereoscopic object displayed in the near-side direction and the far-side direction in a stereoscopic image display apparatus using the II method is explained in detail in H. Hoshino, F. Okano, H. Isono and I. Yuyama, “Analysis of resolution limitation of integral photography,” J. Opt. Soc. Am, A15 (1998), pp. 2059-2065. An ideal stereoscopic image display apparatus in which one element image is seen from one lens or exit pupil is described therein. Therefore, the case where display degradation is caused by lens focus and consequently a plurality of element images are seen with respect to one lens or exit pupil is not described.
A method of reducing the left and right crosstalk by means of image processing is known (see, for example, JP-A 2001-298754 (KOKAI)). This method is a method of reducing the crosstalk by conducting image processing between two parallax images. In this method, averaging processing is conducted as concrete processing and prevention of a multiple image is not described.
A method of improving the resolution of a two-dimensional image utilizing crosstalk is known (see, for example, IP-A 2005-91623 (KOKAI)). In this method, the case where the resolution of the two-dimensional image is improved by crosstalk is described and a measure to counter the degradation of the stereoscopic image caused by the crosstalk is not described (see, for example, JP-A 2001-298754 (KOKAI)).
A structure in which an end part of a lens where the focus becomes dim is not used by placing a lens on the back and barrier printing is known (see, for example, JP-A 09-101481 (KOKAI)). Although this structure always reduces the crosstalk, the crosstalk is not eliminated completely, but moire is caused in some cases by printing black.
In SID004 Digest p. 1438 (2004), it is described that distortion is caused because orthographic projection is conducted in the II stereoscopic display method whereas when viewing an II three-dimensional image the viewer views it in the perspective projection.
When a lens array is used as the optical plate in the stereoscopic image display apparatus, a phenomenon called crosstalk occurs, i.e., information of an adjacent parallax image is mixed into the original parallax light ray, in some cases.